A Sydney tank farm company wanted to replace aging centrifugal pumps used for transferring liquids between storage tanks. Pumps used in tank farms are typically subject to wide variations in operating pressures due to a range of variables including:

• Changing tank levels in suction and discharge tanks.
• Differing properties of the liquids pumped.
• Changing applications such as road tanker unloading, road tanker loading and tank to tank transfer.

Although these varying conditions can be handled by using positive displacement pumps and variable speed drives, cost can sometimes become an issue.

Fixed speed centrifugal pumps are common in such applications due to their relatively low price, high flow rates and maintainability. However, it is vital that the specific characteristics of such pumping systems are understood in order to achieve a reliable solution.

The performance of any given centrifugal pump operating at fixed speed is dependent on the pressure difference between the pump inlet and outlet. Varying applications can cause the pump to operate in a hydraulically unbalanced state. The resulting increase in radial loads and vibration can reduce the service life of the pump, in particular the bearings and seals.

In order to mitigate the effects of variable system pressures ANSI B73 pumps were recommended.

The ANSI B73 pumps are constructed with a large shaft diameter and large axial and radial thrust bearings. The heavy duty construction of these pumps reduces the impact of hydraulic imbalances and provides durability even when operating conditions are less than ideal.

The pumps supplied by Kelair Pumps Australia to the tank farm continue to provide trouble free operation.